Willy Schüep

Content and isomeric ratio of lycopene in food and human blood plasma

Lycopene content up to 520 μgg−1 was measured in a number of tomato-based foodstuffs and meals. (all-E)-Lycopene was the predominant geometrical isomer but varied from 96% to 35% of total lycopene. (5Z)-Lycopene ranged from 4% to 27%. The proportion of (9Z)-lycopene fluctuated between < 1% and 14%. (13Z)-Lycopene and (15Z)-lycopene ranged (together) from < 1% to 7% and the sum of the other (Z)-isomers varied between < 1 % and 22% of total lycopene. It was shown that, during preparation of meals, lycopene undergoes (EZ)-isomerisation, increasing the portion of (Z)-isomers. Compared to food, in human blood plasma the isomeric ratio of lycopene was found to be shifted in favour of the (Z)-isomer fraction, with (5Z)-lycopene as the predominant non-(all-E) component.

Influence of dietary glucan and vitamin C on non-specific and specific immune responses of rainbow trout (Oncorhynchus mykiss)

Abstract A trial was conducted to determine the effect of a combination of dietary glucan and vitamin C on the immune response of rainbow trout. After 3 weeks of adaptation on a control diet (without glucan but containing 150 ppm vitamin C), rainbow trout were fed the experimental diets containing yeast glucan and vitamin C at 150, 1000 and 4000 ppm for 2 weeks and then switched back to the control diet for the following 4 weeks. Macrophage activity (chemiluminescence response), complement activation and lysozyme levels were monitored just after feeding the experimental diets (week 0) and 2 and 4 weeks later. The kinetics of antibody response after vaccination against enteric redmouth disease were determined. The fish were immunised at week 0, at the end of the experimental feeding. Tissue ascorbic acid contents were monitored every 2 weeks and reflected the dietary treatments. No differences were observed in complement levels activated via the classical pathway. Two weeks after feeding the experimental diets, alternative pathway of complement activation and chemiluminescence response were enhanced by high doses of vitamin C. Significant enhancement of macrophage activity was still evident at week 2. No significant differences were observed in lysozyme levels. The specific immune antibody response was enhanced following vaccination, when glucan was also present in the diet.

SIMULTANEOUS DETERMINATION OF RETINOL, TOCOPHEROLS, CAROTENE, LYCOPENE, AND XANTHOPHYLLS IN PLASMA BY MEANS OF REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

Publisher Summary This chapter discusses the simultaneous determination of retinol, tocopherols, carotene, lycopene, and xanthophylls in plasma by means of reversed-phase high-performance liquid chromatography (HPLC). The prevention of certain cancers or cardiovascular diseases has been correlated to the food intake habit and particularly to the composition of nutrition. Among the micronutrients, vitamins—namely, vitamin A, E, and C—and carotenoids belong to the class of substances of interest occurring in food. The way these compounds are being absorbed by the body is of great interest. The concentrations of the individual components present in biological fluids or tissues play an important role in the interpretation of epidemiological studies. The method described in this chapter was developed to assay a large number of plasma or serum samples. It has been tested over a long period of time and has been proven to be robust, efficient, and accurate. In view of the length of epidemiological studies being sometimes in the range of over a decade, special attention has been paid to the stability of the different analytes in the samples under storing conditions as well as to the aspects related to quality assurance. With the present HPLC system, lycopene isomers were only partially resolved and therefore quantified as the grand total related to all-trans lycopene.

Stability of ascorbate-2-sulfate in trout feed measured by HPLC

Abstract A sensitive and simple analytical procedure to quantify ascorbate-2-sulfate (AAS) in fish feed has been established using a reversed phase HPLC system with UV detection. The stability data revealed excellent retention of AAS in mash as well as in pelleted trout feed stored at room temperature and at 37°C over a period of 1 year.

Capillary zone electrophoretic determination of the four vitamin C esters L-ascorbyl-2-phosphate, L-ascorbyl-2-sulfate, L-ascorbyl-2-diphosphate and L-ascorbyl-2-triphosphate in fish feed, plasma and tissue.

A new and fast method for the determination of L-ascorbyl-2-phosphate, the 2-diphosphate, 2-triphosphate and the 2-sulfate ester in feed, fish plasma and tissue samples by capillary zone electrophoresis is described. The substances were extracted with a 200 mM potassium phosphate buffer pH 4.0. Separation was achieved using a 50 microm uncoated fused-silica bubble capillary of 40 cm length to the detector, which was set at 254 nm, and a 80 mM tricine buffer at pH 9.2. Repeatability checked on a trout feed sample revealed a migration time variation of 1.2% (n=24) and an area calculation variation of 2.8% (n=24). Detector response for L-ascorbyl-2-phosphate was linear up to at least 100 microg ml(-1). After administration of a high dose of L-ascorbyl-2-phosphate to rainbow trout, the compound was found in the stomach and intestine but not in plasma, proving a fast conversion to vitamin C.

Measurement of ascorbic acid and erythorbic acid in processed meat by HPLC

ZusammenfassungEine einfache und effiziente HPLC-Methode wird beschrieben, welche die separate Bestimmung der Ascorbinsäure neben der Erythorbinsäure in Fleischwaren ermöglicht. Das System besteht aus einer Umkehrphasensäule, einer mit einem Ionenpaarbildner modulierten mobilen Phase und UV-Detektion. Das Verfahren wurde an einer Reihe verschiedener Proben getestet und erwies sich als zuverlässig und reproduzierbar.SummaryA simple and efficient HPLC method is described to measure both ascorbic and erythorbic acid separately in processed meat products. The system used consisted of a reversed-phase column, a mobile phase containing an ion-pairing agent and ultraviolet detection. The procedure, which was checked on a variety of samples, was found to give reproducible and reliable results.